Unformatted text preview: Physics 212
Le cture29
CourseRe w vie
e • TheTopics You Want to S e
– – – – – – – – Ele ctric Fie lds/Gauss’ Law/Pote ntial (33% ) Faraday’s Law (14% ) RC /RL C ircuits (12% ) ACC ircuits (10% ) Ge e Optics (10% om tric ) Magne Fie & Force (9% tic lds s) Ele ctrom tic Wave agne s/Polarization (9% ) DCCircuits (3% ) Physics 212 Le cture29, S 1 lide Music
Who are the Artists? A) B) C) D) E) Whitney Houston and Tina Turner Nina Simone and Patti LaBelle Etta James and Bonnie Raitt The Dixie Cups Marcia Ball, Irma Thomas, Tracy Nelson
BB BB THANKS FOR YOUR REQUESTS I WILL BE CHECKING THEM OUT… Why? Why? Marcia Ball was requested ! Marcia I’ve been thinking about New Orleans… I’ve New Orleans Jazzfest Poster from last year The Sweet Soul Queen of New Orleans: Irma Thomas
Physics 212 Le cture29, S 2 lide Physics 212
Le cture29
CourseRe w vie
e • TheTopics You Want to S e
– – – – – – – – Ele ctric Fie lds/Gauss’ Law/Pote ntial (33% ) Faraday’s Law (14% ) RC /RL C ircuits (12% ) ACC ircuits (10% ) Ge e Optics (10% om tric ) Magne Fie & Force (9% tic lds s) Ele ctrom tic Wave agne s/Polarization (9% ) DCCircuits (3% ) Physics 212 Le cture29, S 3 lide 1
I I1 I – I1 L L dI1 + IR − V = 0 dt 2 dI1 − ( I − I1 ) R = 0 dt IR = V − L dI1 dt 1
30% 2 L dI1 dI − V + L 1 + I1R = 0 dt dt dI1 2L + I1R = V dt S gy: Back to First Principle trate s
e te ine re • Thetim constant is de rm d froma diffe ntial e quation for thecurre through theinductor. nt nt d • Equation for curre through inductor obtaine fromKirchhoff’s Rule s f rom τ= " L" 2 L = " R" R Physics 212 Le cture29, S 4 lide BB Horizontal com nts cance pone l E fromtop arc points down E frombottomarc points up Etotal points down Top arc produce sm r horizontal com nts s alle pone C alculation:
Etop = ∫ dq 4πε0 r 1
2 cos θ
θ θ top Q Etop = 2 ∫ rdθ cos θ 2 2 rθ 4πε0 r top 0 sinθ θ Etop = Q sin θtop 4πε0 r 2 θtop θ
Physics 212 Le cture29, S 5 lide BB Pote ntial Ene is a m asureof work doneby E fie rgy e ld S rical sym e & Gauss’ law phe m try E = 0 iinsideshe nside ll E = 0 insideshe inside ll No work doneto m q ove No No changein pote ntial e rgy ! ne
Physics 212 Le cture29, S 6 lide BB ALWAYSS ALWAYS TART FROM DEFINITI ON OF POTENTIAL POTENTIAL a ∆V = − ∫ E ⋅ dr
(A) (B)
1 2Q 3Q − 4πε0 a b 1 3Q 2Q − 4πε0 b a (C) 0 (D) (E) 1 2Q 2Q − 4πε0 a b 1 2Q 2Q − 4πε0 b a b S rical sym e & Gauss’ phe m try law de rm s E law te ine 1 2Q a < r < b: E = 4πε0 r 2
a dr 2Q ∆V = − 4πε0 ∫2 br ∆V = 2Q 1 1 − 4πε0 a b Physics 212 Le cture29, S 7 lide BB (A) (B) 1 2Q 4πε0 a − 1 2Q 4πε0 a (C) 0 (D) (E) 1 3Q 4πε0 b − 1 3Q 4πε0 b S rical sym e & Gauss’ phe m try law de rm s E law te ine r < a:
E =0 ∆V = − ∫ E ⋅ dr = 0
0 a Physics 212 Le cture29, S 8 lide C hargem beinduce ust d t o insureE = 0 within conducting she conducting ll
BB S rical sym e & Gauss’ phe m try law de rm s E law te ine Qenclosed ∫ E ⋅ dA = ε0
(A) (B)
4πa 2 + Q1 4πa
2 − Q1 (C) Q2 − Q1
2 (D)
2 4π (b − a ) 4πb 2 4πb 2 + Q1 − Q1 E ⋅ 4πr 2 = 0
Qenclosed = Q1 + (−Q1 ) (E) σ= 4πb 2 − Q1 Physics 212 Le cture29, S 9 lide BB Physics 212 Le cture29, S 10 lide 10 BB ALWAYSS ALWAYS TART FROM DEFINITI ON OF POTENTIAL POTENTIAL b ∆V = − ∫ E ⋅ dr
0 Bre inte into two pie s ak gral ce a b ∆V = − ∫ E ⋅ dr − ∫ E ⋅ dr
0 a
conductor: = 0 iinsulator: i 0 nsulator: sam for e sam conductor & insulator insulator
Physics 212 Le cture29, S 11 lide 11 BB 76% C nt induce be urre d causeflux is changing Flux is changing be auseB is changing At t = 5 se conds, B is positive but de asing , cre Le law: e f induce to opposechangethat brought it into be nz’ m d ing I nduce curre m producepositiveB fie d nt ust ld PositiveB fie produce by counte ld d rclockwisecurre nt
Physics 212 Le cture29, S 12 lide 12 BB 62% Flux de finition: Faraday’s law:
dB = −2T / s dt Φ = ∫ B ⋅ dA = BA = Bwh ε =− dΦ dB = − wh dt dt I= ε 9/5 = = .012 A R 150
Physics 212 Le cture29, S 13 lide 13 BB 65% C nt is de rm d by tim rateof changeof theflux urre te ine e dΦ/dt is de rm d by dB/dt te ine dB/dt (6s) = dB/dt (5 s) = 2 T/s Theinduce curre at t = 5s and t = 6s aree d nts qual Physics 212 Le cture29, S 14 lide 14 Phasor diagram at t = 0 What is VC at t = π /(2ω )
(A)
+ VC max sin α − VC max sin α (C) (D) + VC max cos α − VC max cos α α BB (B) Phasor diagram at t = 0
VR VC α
VL Voltageis e Voltage qual to proje ction of phasor along ve rtical axis ve
Physics 212 Le cture29, S 15 lide 15 ...
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 Spring '08
 Kim
 Magnetism, Force, Trigraph, ele ctric fie, Magne Fie & Force, ctric Fie lds/Gauss

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